java.lang.NullPointerException at com.opensymphony.xwork2.util.LocalizedTextUtil.findText(...

为了防止CSRF攻击，在struts2的form表单中使用<s:token/>，在拦截器里添加了<interceptor-ref name=”token”/>，结果发现抛出下面的异常：

java.lang.NullPointerException

at com.opensymphony.xwork2.util.LocalizedTextUtil.findText(LocalizedTextUtil.java:630)

at com.opensymphony.xwork2.util.LocalizedTextUtil.findText(LocalizedTextUtil.java:606)

at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:210)

at com.opensymphony.xwork2.TextProviderSupport.getText(TextProviderSupport.java:139)

at org.apache.struts2.interceptor.TokenInterceptor.getErrorMessage(TokenInterceptor.java:182)

at org.apache.struts2.interceptor.TokenInterceptor.handleInvalidToken(TokenInterceptor.java:166)

at org.apache.struts2.interceptor.TokenInterceptor.handleToken(TokenInterceptor.java:151)

at org.apache.struts2.interceptor.TokenInterceptor.doIntercept(TokenInterceptor.java:142)

at com.alibaba.search.scc.web.interceptor.SccTokenInterceptor.intercept(SccTokenInterceptor.java:42)

at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)

at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)

at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:562)

at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)

at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)

我的用法照理讲应该是官方的用法，按照异常堆栈查看struts2源码，发现问题在这里：

TokenInterceptor.java

Java

@Inject
    public void setTextProvider(TextProvider textProvider) {
        this.textProvider = textProvider;
    }

    protected String handleInvalidToken(ActionInvocation invocation) throws Exception {
        Object action = invocation.getAction();
        String errorMessage = getErrorMessage(invocation);

        if (action instanceof ValidationAware) {
            ((ValidationAware) action).addActionError(errorMessage);
        } else {
            log.warn(errorMessage);
        }

        return INVALID_TOKEN_CODE;
    }

    protected String getErrorMessage(ActionInvocation invocation) {
        Object action = invocation.getAction();
        if (action instanceof TextProvider) {
            return ((TextProvider) action).getText(INVALID_TOKEN_MESSAGE_KEY, DEFAULT_ERROR_MESSAGE);
        }
        return textProvider.getText(INVALID_TOKEN_MESSAGE_KEY, DEFAULT_ERROR_MESSAGE);
    }

@Inject

public void setTextProvider ( TextProvider textProvider ) {

this . textProvider = textProvider ;

}

protected String handleInvalidToken ( ActionInvocation invocation ) throws Exception {

Object action = invocation . getAction ( ) ;

String errorMessage = getErrorMessage ( invocation ) ;

if ( action instanceof ValidationAware ) {

( ( ValidationAware ) action ) . addActionError ( errorMessage ) ;

} else {

log . warn ( errorMessage ) ;

}

return INVALID_TOKEN_CODE ;

}

protected String getErrorMessage ( ActionInvocation invocation ) {

Object action = invocation . getAction ( ) ;

if ( action instanceof TextProvider ) {

return ( ( TextProvider ) action ) . getText ( INVALID_TOKEN_MESSAGE_KEY , DEFAULT_ERROR_MESSAGE ) ;

}

return textProvider . getText ( INVALID_TOKEN_MESSAGE_KEY , DEFAULT_ERROR_MESSAGE ) ;

}

出问题的是textProvider.getText方法，原因是textProvider中的bundle和class是空的，为什么是空的呢？可以看到setTextProvider方法上有一个@Inject注解，这个注解告诉了struts2需要注入一个类型为 com.opensymphony.xwork2.TextProvider 的实例，因为struts jar包里面的 struts-default.xml 中默认的配置是：

Java

<span class="code-tag" style="color: #000091;"><bean type=<span class="code-quote" style="color: #009100;">"com.opensymphony.xwork2.TextProvider"</span> name=<span class="code-quote" style="color: #009100;">"struts"</span> class=<span class="code-quote" style="color: #009100;">"com.opensymphony.xwork2.TextProviderSupport"</span> /></span>

< span class = "code-tag" style = "color: #000091;" > & lt ; bean type = < span class = "code-quote" style = "color: #009100;" > "com.opensymphony.xwork2.TextProvider" < / span > name = < span class = "code-quote" style = "color: #009100;" > "struts" < / span > class = < span class = "code-quote" style = "color: #009100;" > "com.opensymphony.xwork2.TextProviderSupport" < / span > / & gt ; < / span >

所以默认注入的就是TextProviderSupport实例对象，而这个bean中没有默认指定class和bundle，这就导致了textProvider.getText方法抛出空指针异常。

根据官方文档中的说法，可以自己实现TextProvider，形如：

<bean class=”org.demo.MyTextProvider” name=”myTextProvider” type=”com.opensymphony.xwork2.TextProvider” />

<constant name=”struts.xworkTextProvider” value=”myTextProvider” />

换个方式解决问题：

如果上面的getErrorMessage方法中执行了if语句里面的内容就不会走到textProvider.getText方法那里去，所以可以尝试让action的类型属于TextProvider，在TextProvider上ctrl+T可以看到其实现类上有ActionSupport类，所以这就知道了只需要让action类继承ActionSupport类即可避免抛出上面的空指针异常。

当然，既然进入到handleInvalidToken方法里面来了，那就需要为返回值INVALID_TOKEN_CODE（“invalid.token“）配置出错页面，形如：

XHTML

<global-results>
    <result name="invalid.token" type="dispatcher">
        /templates/error/illegal_operate.jsp
    </result>
</global-results>

<global-results>

<result name = "invalid.token" type = "dispatcher" >

/templates/error/illegal_operate.jsp

</result>

</global-results>